Biologists, neurologists and an assortment of other scientists reveal in ever more detail the workings of our bodies. Books, magazines, journals and videos brim with illustrations of these workings, from the quantum level up to the neural networks of brains that govern our capacities to think, see and so on. But for all this science one thing remains a mystery, a puzzle so enigmatic that we can only formulate it by figure of speech. It is to ask: What is it that gives us an inner life? We are after all made of the same materials in kind as rocks and toaster ovens.

With respect to the concept of life more generally, it was once thought that life is literally, rather than metaphorically, a force – what was called ‘élan vital’ – something we have and rocks do not. But eventually scientists disabused us of this vitalism, the idea that life must be explained by postulating some such life force, a species of ensoulment. All the processes that consititute a living thing are ultimately understood to be mechanical in nature, from the duplication of strands of DNA in the cell to the firing of synapses in the brain. Yet still we suspect that we are more than the sum of mechanical processes. Again to revert to metaphor, the tugs on hearts, pangs of despair, dizziness and all sorts of other ‘inner’ episodes have to them a quality, a feel, that is not explained by chemical reactions. We are not just biological machines.

As a philosopher of mind I have confronted this mystery in terms of what is called the problem of consciousness. It is to ask whether or not it is possible for the natural sciences to explain this additional ingredient of us, the so-called what-it-is-like to be a human being, to borrow the term made famous by the American philosopher Thomas Nagel. Within this refined philosophical debate loaded with technical terms like supervenience, qualia and numerical identity, some have argued that all such metaphorical talk is about nothing, that we are in the end no more than physical processes. Others vehemently maintain that this extra ingredient is real and argue that we ought to conclude some of the features we possess are simply not physical – they lie beyond the scope of scientific inquiry, as we traditionally practise it at least.

One of the most subtle positions within this philosophical debate – not to suggest that others are not subtle – is offered by another American philosopher John Searle. Searle insists that this ingredient is real but argues that it is a specifically biological phenomenon.[i] By this he means that there is something peculiar about our biological processes themselves that results in our having such an ‘inner life’. Alas, he also argues that this peculiarity is inscrutable. We may eventually be able to isolate and identify those especial biological processes that produce an inner life in us, but the phenomenon itself is such that we cannot determine why they do so. Searle’s conclusion is echoed by many other philosophers, though certainly not all, who hold that the very nature of this inner life, or ‘consciousness’ as it is often called, means it cannot be explained away as such-and-such physical processes.

Perhaps we have reached a dead-end with respect to philosophical theorising; where by her theory the philosopher aims to provide a precise enough analysis of the concept of inner life that we can identify its place in nature. Once this is accomplished we can begin to figure out how it fits in the processes that demarcate life. But whether such an analysis is ultimately achievable or not, I don’t think this apparent dead-end implies we cannot make sense of inner life in other ways. After all there are many ways of telling stories about something in the world that give us a better understanding of it besides by formal theory. So instead of trying by philosophical analysis to wring out our vague metaphorical descriptions of inner life we can embrace them and try to build on them.

Consider the concept of love. British science writer Colin Tudge was inspired to write a column on this markedly unscientific subject after reading a collection of poems by W.H. Auden titled Tell Me the Truth About Love – the publication of which was spawned by the popular film Four Weddings and a Funeral that featured one of these poems. Tudge remarks: “What we need to do is to understand what we find of value in love. We cannot explain what love is unless we understand what we value in it. Evolutionary, psychoanalytical or theological accounts of the function of love inevitably fall short of explaining the value we find in the emotion.”[ii] Auden himself spent his entire adult life trying to understand love through his poetry. We gain something in reading his poems on the subject, a better understanding of sorts. With respect to the concept of inner life I do not have in mind a purely poetical inquiry of any kind. That is but one route. Rather, I think a place to start is with Searle’s observation that consciousness, as he calls it, is biological. While Searle thinks of the biological as being ultimately a set of mechanical processes, we can instead focus on the notion of the biological more broadly. I shall offer a genealogy of inner life, aimed at understanding it by retracing it back to its inception. To do this I shall talk of inner life not in terms of consciousness or phenomenology, but as something more basic. What this amounts to is hard to describe initially. For now I shall characterise it as that which all living things share.

The Land of the Living

The great Aristotle had much to say about the phenomenon of life.[iii] In particular he thought that immortal beings, that he presumed to exist, are alive even though they don’t have the faculties required by mortal beings. These are for example the capacities to metabolise and to take in or produce food. Aristotle termed these the faculties of the nutritive soul, which are shared by all living things (by our lights anyhow). If these essentially mechanical powers are not the basis for life according to Aristotle, then what is? Aristotle held a teleological worldview. He thought that everything in nature is the way it is in virtue of fulfilling its form, that is, its principle of existence governed by its end – what might roughly be described as its raison d’être. Everything in nature exists for a purpose, as part of a hierarchy of purposes or ends (telos). A being’s purpose determines its shape, functions and so on. Living things, by this measure, are alive because of their form. Immortal beings by their nature exist eternally and so there is no need for their having faculties to maintain themselves, as by contrast must be the case for mortal beings. Individual mortal beings come and go. They come into being, as we all know, through being reproduced by an earlier individual or pair thereof. And so one of the basic faculties of the nutritive soul is to reproduce, i.e., to replicate itself. Indeed all living things reproduce themselves. That, for Aristotle, is the essence of living things as we understand them. Life is the power to reproduce.

On reflection the power of reproduction is peculiar. Most of the stuff found in the universe is inert in this respect. There is only one bit of stuff – that we know of at least – that does reproduce itself, that is, that has the basic characteristic of replicating itself and thus replicating its capacity to replicate itself. That bit of otherwise inert stuff is the complex molecule DNA and its cousin RNA. How it came to pass that these peculiar bits of matter emerged is still largely conjecture.

Biochemist Nick Lane has tracked much of the research on the origin of life in the decades subsequent to the discovery of DNA.[iv] Lane reports that a most plausible hypothesis for how DNA was first formed is that it happened under the sea in volcanic hydrothermal alkaline vents. These are gentler versions of the more acidic vents known as black smokers, which violently spew out superheated gases. They have existed for as long as the earth and sea themselves have been around. The constant flow of minerals in these alkaline vents produces a fine labyrinth of cell-sized chambers and passages. This uncommon environment is likely where the first living cells originated. Two key conditions are met there. First there is the rich supply of chemicals to jump start life’s signature engine, namely the so-called Krebs cycle. Second there are the physical conditions which allow nucleotides to concentrate and thus to be able to combine and recombine into long chain molecules known as RNA that, as noted, have the capacity to replicate themselves.

The processes by which the chambers in these alkaline vents were formed became incorporated into the soup of chemicals with RNA molecules. Their incorporation ultimately produced a stand-alone cell with its own protective shell or membrane. The cell-like structure of the vents themselves, in other words, furnished the conditions for the first living proto-cells. RNA’s crucial reactivity also means that it is too unstable to allow for sustainable cells. However with a few minor changes, e.g., dropping an oxygen atom, RNA turns into one of the two constituent strands of the DNA molecule. DNA is far more stable. Accordingly this double helix molecule came to predominate, and the basic architecture of all living cells was set.

The details of this hypothesis are likely to change and perhaps someone will eventually advance a different even more plausible hypothesis. For example, the presence of UV radiation may well be a necessary condition for the initial formation of the cell, and that rules out its occurrence in vents deep under the sea.[v] Either way the story shows that very probably DNA and living cells arose accidentally from a fortuitous set of circumstances. And one must keep in mind that these conditions need only have occurred once for life to have got started according to such an account.

But more importantly I aver, the distinctive characteristic of DNA, namely its ability replicate itself, suggests a new crucial qualitative division of stuff in the world. The advent of this peculiar self-replicating stuff effectively introduces into the world ends. DNA ‘aims’ to replicate itself. Of course it does not do so by design, i.e., consciously, as it is indeed an accidental feature of the molecule. Nonetheless it becomes the first thing to which we can apply what British philosopher Gilbert Ryle called an ‘achievement’ verb.[vi] These are verbs that presuppose a goal by which the action so described can be said either to succeed or fail. For example, your being said to look for a house assumes that you will either succeed or fail in the action. These verbs stand in contrast to what Ryle called ‘process’ verbs such as ‘to flow’; where something’s flowing does not entail any purpose or end. In a world inhabited only by the basic physical constituents like gases, geological formations and so on, there is nothing to which one could assign a goal. With the advent of DNA there is something that can be said either to have succeeded or failed in replicating itself, even if it is not literally trying to do so. One can think of ‘survive’ in this respect as the original achievement verb.

So we can now understand a cell as having a goal. That goal is best described as to survive. Survival is the ultimate end of all living things. While life most likely started in the form of single-celled organisms, we can also tell a good story about how co-opting between cells led to the evolution of multicellular organisms, all the way up to us and other higher animals. However complex these organisms have become, they can all be characterised as what Richard Dawkins, author of The Selfish Gene, famously called ‘survival machines’ for their DNA.[vii] All organisms have arisen as a means for the DNA, defined by the codes stored in them, to replicate themselves, since it is their very replication that spawns their replication. Every organism has evolved as an adaption to the environment. Any organism that has the resources to survive in an environment long enough to replicate itself succeeds in replicating itself. Those that do not survive cease to exist. What exists, therefore, are those organisms that have successfully adapted. Here we simply describe the process of natural selection. It is a process driven by DNA’s replicability.

Interestingly, one of the resources of an organism that can aid in its survival in a particular type of environment is other like organisms, that is, its kith and kin. Insofar as cooperation between fellow organisms promotes survival the proclivity to do so is selected for. The result is that organisms have evolved to rely, to varying extents, on communitarian cooperation. For the DNA this is just another ‘strategy’ or outcome of their drive to survive, i.e., to replicate themselves by whatever means. Such cooperation in its extreme has led to the evolution of eusocial organisms, e.g., ants and bees. These superorganisms – the colonies that are constituted by bees and ants – rely on individuals giving up their capacity to reproduce in the interest of raising their close relatives, i.e, the offspring of the queen, much of whose DNA they share.[viii]

Inner and Outer Life

We all are acquainted, of course, with the drive to survive on an individual basis. It is expressed in extremis by primitive fear, where the body is alerted to an immediate danger and thoughts and actions quicken. But this drive operates on us when making mundane decisions too, wherein we seek security, comfort and even pleasure – anything conducive to prospering and hence survival. And it is this same drive that Dylan Thomas alludes to in his well-known poem Do not Go Gently into that Night, describing how even in old age near death this drive remains. The poem ends with the line: Rage, rage against the dying of the light. The life force, one might say, of DNA’s drive to replicate itself is the source of this rage. It is a raging, or madness perhaps, that comes from deep within us, quite literally from every cell in the body.

The rage Dylan Thomas describes is largely without focus, a lashing out as the world darkens for a dying person on the cusp of oblivion. But as a rule the rage of the organism finds a target, namely its immediate environment with all its dangers. The division between self-replicating stuff and inert stuff, in other words, presents itself in the form of a battle between organism and world. The world in this sense is the other, that which is not the organism. The life force is manifested as this division, the dichotomy of self and other.

To illustrate the emergence of this dichotomy consider the case of euglena. These are micro-organisms, of the family euglenoidae, that live in water or soil.[ix] Each euglena has a flagellum – a hair-like appendage it uses to propel itself. Some species of this organism contain chloroplasts, and so they make their own fuel by photosynthesis. The euglena also has a primitive means of detecting light, an organelle (a functionally significant element of a cell) called an ‘eyespot’. If it is in darkness it begins to move around randomly in order to ‘seek out’ light. Those individuals that are disposed to move towards light have been naturally selected.

These creatures are not conscious – all their reactions are instinctive i.e, innate behaviour. But they do react to their environment. Each euglena acts in a goal driven manner, that is, to seek light in order to produce energy and go on to replicate its DNA. In other words, it has its own end. In contrast to euglena a piece of inert matter, e.g., a rock, does not have an end of course. A rock ‘owns’ nothing in this sense. It has no self-interest. I’m not suggesting that the contrast between a rock and euglena is that the latter has an inner life and a rock does not. Neither has an inner life. There is, nonetheless, a crucial qualitative difference between them. Nothing about a rock and euglena in physical terms speaks of this difference. In the case of euglena a contrast exists between it and the world. This contrast does not exist for a rock.

While a single-celled organism like euglena – or paramecium to give another example – has no inner life, clearly anything that does have one shares with these organisms this contrastive quality. An inner life, as we understand it here, is based on the biological characterised in terms of reproducibility. Accordingly, an organism has an inner life on condition that it is living in this sense. So what is missing from euglena that procludes it from having an inner life? What is the sufficient condition (that which is enough to give an organism an inner life in this context) that euglena lacks and that we possess? There is none. It is best to think of having an inner life as by degree, gradated. At the very bottom end of this continuum we find euglena and paramecia that are so simple they have no inner life to speak of, and much farther along we find elephants, dolphins, chimpanzees and ourselves, endowed with rich inner lives.

Looking at the phenomenon of an inner life from this genealogical perspective helps us to understand why it is not easy to explain it in the mechanistic terms, why, in other words, we must revert to figurative speech to talk about it. The physical processes of our body themselves do not account for the contrast between the outward actions of an organism and its reciprocal inner life. Moreover, for euglena the outside world consists in light and not much else – that is all the creature ‘detects’. And so its inner world is correspondingly meagre, next to non-existent. By contrast, we can discern countless qualities and objects in the outside world, given our vastly more complex bodies. Thus we have a correspondingly much richer inner life. The relevant difference is the degree of interaction we have with our environment versus Euglena. It is this vastly complex interaction between us and the world that explains the richness of our inner lives, and not the physical processes that realise that interaction.

We’ve noted that some species of euglena contain chloroplasts and so produce their own food. These are plant-like organisms. But other species are heterotrophs, meaning that they obtain energy by feeding on other organisms. These euglena are animal-like. Now, I have argued that while euglena have no inner life to speak of, they do possess the contrastive quality that is the basis of an inner life. Plants, one might object, don’t possess an inner life, no matter how complex their multicellular forms might be. Commonsense tells us that even the mightiest trees lack an inner life. This contrastive quality, therefore, does not appear to be sufficient for an organism to have an inner life, contrary to my conclusion. If it were, then trees would have to be thought to possess an inner life.

What this worry points to is a bifurcation of the notion of an inner life that I touched on at the beginning. By ‘inner life’ we often have in mind our own case. Present ‘inside’ each of us are complex feelings, a phenomenology to use a more technical term. Above I have talked instead of an ‘inner life’ in the sense that organisms own their actions, are fundamentally self-oriented. This self-orientation results from interacting with the ‘outside’ environment. Thus ‘the self’ here names that which arises in contrast with this outward interaction. It is inner in this contrastive sense. Now, you might respond that plants have no inner life in this sense either. As inanimate objects they do not react to their environment in a manner that can be described as self-interested. They are simply blown hither and thither, so to speak.

This response, however, confuses these two distinctive uses of the term ‘inner life’ outlined above. Yes, trees, for example, are not conscious in any sense in which we are so. But trees are living things, and as such they do have inner lives insofar as they have interests. Casual observations of trees does indeed tempt one to suppose they never really act, even compared to plant-like species of euglena – at least they move about in ‘search’ of light. But it is odd to suppose that it is more plausible to believe a very simple plant-like micro-organism has an inner life than to believe a tree does. The salient difference between these two types of organisms is scale in relation to time. Trees do in fact act, but their actions are at a very much slower pace. That makes them imperceptible from moment to moment.

The German forester turned author, Peter Wohlleben, presents a detailed account of how trees act, and act in a self-interested manner no less. Now many who have picked up Wohlleben’s book The Hidden Life of Trees have likely felt uncomfortable about, and even dismissive of, his talk of trees as having feelings, communicating and caring for one another for example.[x] Such talk does betray an excessive degree of anthropomorphising by the author. But this anthropomorphising is otherwise heuristically very effective. It is used by the author to emphasise that trees do act. Acting is here understood as physical changes that are directed towards self-interest, e.g., a euglena moving at random using its flagellum in the darkness in order to encounter light. These actions are often referred to as behaviours.

A tree, as a body, does not act by changing location in this way of course; rather it acts by means of growing, i.e., directed cell production. A common instance of this is the forming and dropping of leaves by deciduous trees on a seasonal basis. Its cyclical nature is behavioural because it is not just a matter of the division of cells up until the point of maturity. Further, as Wohlleben points out, many deciduous trees extract the chlorophyll in their leaves, and store it in their branches – hence their change in colour as winter closes in.[xi] This behaviour enables the tree to economise on the production of chlorophyll for the next spring. To do this requires trees to be sensitive to light and temperature. Likewise, tree roots are positively geotropic, that is, they direct their growth downwards. This is possible due to an organelle in trees’ cells called a statolith that is sensitive to gravity. In general trees clearly have a nuanced set of interactions with their environment. Wohlleben describes an enormous range of these interactions. And again, the richness of an organism’s inner life correlates with the complexity of its interaction with its environment.

Varieties of Inner Life

What seems clear is that the interactions of plants in general with their environment result directly from cellular processes, such as the statolith organelle detecting gravity. Another example is the elongation of certain plant cells, that enables the plant to grow in particular directions, is stimulated by the hormone auxin; this is produced in the apical meristem – the tips or apices of the plant from where cells divide and grow outward, e.g., in the leaves and stems. One might say that a plant’s actions are slow and dissipated. By contrast animals have developed centralised behaviours in order to cope with the real-time actions they need to make in order to survive. Again, an example of a simple organism illustrates the idea well. Roundworms or nematode worms are the most numerous animals on earth, found in abundance in many soils. It has a brain consisting in a few hundred neurons. That’s tiny of course – even the humble bee (excuse the pun) has a brain with one million neurons.[xii] The worm only has a lifespan of a few days and one of the principal dangers it faces is the bacteria Escherichia Coli (commonly known as E. coli). These bacteria are toxic to the worm. The newborn worm, once it encounters the bacteria, retreats and remembers the signature toxin. Thus in the future it knows to avoid the bacteria. This example points to the fact that a fundamental purpose of brains is to learn about the environment in order to increase the chance of survival.

The larger and more complex an organism is the greater are the number of challenges it faces in its survival. Accordingly, many creatures have developed multiple sense organs to navigate around their world. All of the information provided by a creature’s senses must be centrally processed in order that it acts in a coherent manner. Once again, the complexity of a creature’s interaction with its environment leads to a correspondingly rich inner life; but in addition its richness is amplified by the centralisation of the creature’s actions through a brain. So even though trees have complex interactions with their environments the dissipated nature of their actions means that they do not ‘experience’ the world as such, as animals do.

As mentioned, in presenting this genealogy of inner life I have distinguished between two uses of the term. Sometimes we use the term to allude to the sort of phenomenology we humans have. I gave the examples of such episodes as pangs of despair, tugs on hearts and dizziness. But through most of the discussion I have primarily used the term to allude to the self, understood as that which stands in contrast to an organism’s outward interactions with the world. Insofar as an organism’s physical movements and changes are aimed at survival – and can accordingly be characterised as self-interested – it stands in contrast to the outside world, and hence I call this contrast ‘inner’. I want to conclude by relating these two uses of the term.

Essentially I have assumed that life has two aspects to it, an outward and an inward aspect. This directional characterisation of life is helpful. I have resisted talking of this inward aspect, i.e., inner life, as a kind of natural feature of organisms. This thought relates back to my assertion that the advent of DNA spelled a new qualitative division of things in the world, namely between those things that are self-oriented in virtue of being self-replicating and those things that are inert in this respect. This division is not the result of a new kind of physical stuff arising in the world, of some novel feature of something emerging in the universe. Yes, it resulted from the chance formation of a self-replicating molecule, but the physical processes underwriting this replication are not themselves novel. Rather, the division resulted from the addition of this new directional dimension that the products of DNA, i.e., unicellular and eventually multicellular organisms, have acquired. Being a euglena or an oak tree involves an outwardness and a reciprocal inwardness. This directionality to existence does not hold for inert forms of matter, which are effectively describable in physical terms alone. So if one were to list all the physical features of the world – obviously an ideal rather than anything that can be practically done – nothing would be said about an inner life. What I hope to have shown by way of this genealogy is that the irreducibility of inner life to physical or mechanistic processes is to be expected. It does not indicate that an inner life is mysterious, i.e., an apparently non-physical phenomenon. Again, it is not a phenomenon or natural feature, rather ‘inner life’ alludes to a way of existing.

Finally, with respect to the distinction between inner life understood in phenomenological terms and not, I have suggested that this distinction is not a matter of kind but of degree and complexity. Phenomenology is inner life as it is manifested by brained creatures, i..e, animals. It results from the centralisation and amplification of the actions of such creatures. This amplification expresses itself in what we call experiences, namely those episodes of our inner lives that are described in terms of sensations. Admittedly this is a vague characterisation of what is an immensely complex ‘phenomenon’. But what has stymied our analyses of inner life understood in terms of what we call ‘consciousness’ is their top-down approach. Traditionally such analyses start by considering the buzzing mass of our own phenomenology. We have tried to make sense of a plethora of these overlapping subjective feelings, from toothaches to dizziness to the redness we experience looking at a tomato, say. How do we explain all THIS in terms of brain processes etc.? My approach instead has been bottom-up, that is, to start by considering what the inner life of the simplest organisms consists in. From there I have tried to tell a story about how we get from the inner lives of these organisms – which are in themselves next to nothing – to buzzing complexity of our own conscious experience. I hope to have shown this non-traditional approach has much promise. It may go a long way to aiding our understanding of what has hitherto seemed to be a mystery.

Endnotes

[i] See John Searle’s The Rediscovery of the Mind, Cambridge, MA: The MIT Press, 1994.

[x] Peter Wohlleben, The Hidden Life of Trees: What They Feel and How They Communicate, Vancouver, BC: Greystone Books, 2016. Originally published in German under the title Das geheime Leben der Bäume, Munich: Random House GmbH publishing Group, 2015.

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